Pressure reduction valve for bottled gas systems



Jan. 22,1946. H. e. MARTIN, JR 2,393,545

PRESSURE REDUCTION VALVE FOR BOT'iLED GAS SYSTEMS Filed Aug. 50, 1 ,41 7

Patented Jan. 22, 1946 PRESSURE REDUCTION VALVE FOR BOTTLED. GAS SYSTEM?Henry G. Martin, Jr., New Orleans, La., assignor to Standard OilDevelopment Company, a corporation of Delaware I Application August 30,1941, Serial No. 408,949

v 2 Claims.

This invention relates to a method and apparatus for storage anddispensing of highly volatile liquefied gases and relates moreparticularly to a method and apparatus for storage and dispensingofmixtures of highly volatile liquefied gases.

In gas systems (such as home butane installations). which are suppliedby the evaporation of liquefied hydrocarbons from pressure containers,the gas is usually withdrawn from the top of the container and expandedthrough a suitable pressure reducing valve. When a mixture ofhydrocarbons such as butane and propane is used, this method ofwithdrawing the gas causes the mixture within the container to becomeprogressively richer in the less volatile components and consequentlylowers the vapor pressure of the remaining liquid mixture. One method ofovercoming this diillculty is to withdraw liquid from the bottom of thecontainer and to vaporize it in a pressure reducing valve. Due to thefact that such hydrocarbon stocks usually contain traces of moisture,the low temperature brought about by the vaporization of the hydrocarbonmay cause the pressure reducing valve to "freeze up."

1 idly as required.

An object of this invention is to provide means for withdrawingsubstantially uniform mixtures of volatile gases from the container eventhough the container be partiallylor wholly filled.

Another object of this invention is to provide an arrangement ofapparatus so that the pressure reducing valve is not subjected toextreme low temperatures.

A further object of this invention is to provide a method for vaporizingliquefied gases so that the main source of heat for vaporization is thelatent heat of condensation of gases similar to those being vaporized.

These and other objects of the invention may be understood by-readingthe specification with reference ,to the accompanying drawing wherein isa vertically sectional view of aninstallation embodying the invention.

For purpose of description with reference to the drawing, it is assumedthat a mixture oi liquefied normally gaseous hydrocarbons is stored in acylindrical tank I of any suitable capacity to the level 2. The tank maybe arranged vertically or horizontally and it is preferred to beinsulated by burying underneath the surface of the ground below thefrost level; however, it may be covered with a suitable insulatingmaterial, such as asbestos, magnesia, etc.,'provided that an externalsource of heat is employed when the tank is so insulated other than byburying in the ground. This tank'may be filled with liquefied gas underpressure by means of pipe 3 provided with valve 4 and pipe 5. Avapor-tight chamber 8 is arranged above tank I and is con nected theretoby line 6 which is provided with valve 1. Pipe 9, provided with valveI0, serves as an outlet for chamber 8.

The means for withdrawing the charge from tank I for consumptionincludes pipe 5, which is provided with a hand operated valve I2, aservice pipe I5, which may be connected to suitable means not shownrequiring a supply of vapors from tank I', and an automatic pressurereducing valve II connecting pipe 5 with service pipe I5. Valvessuitable for use as the automatic regulator valvev II are well known tothe art and commerciallyavailable; such valves are conventionallyconstructed either as spring operated pressure reducing valves orweighted lever pressure regulator valve and are shown, for example, inthe Chemical Engineers Handbook, McGraw-Hill Company, 1934, pages 1659and i 1660. The dimensions of pipes 5 and I5 are not critical but, forbest operation, these pipes should not be excessively long and shouldpreferably be of a diameter only sufficiently large to transfer theamount of liquefied gas from tank I required tomeet the load on thesystem with a minimum of pressure drop. Pipe 6 should be of such sizethat vapors may easily passfrom tank I to chamber 8 without interferingwith the return of liquid from chamber 8 to tank I.

In operation, it is preferred to charge the tank with liquefied gas asindicated-in the drawing with the liquid level 2 of the charge somewhatbelow the top of the tank; the vapor space It in the upper part of thetank is usually maintained as it is required for safe operation. Withthe tank charged as shown, when fuel is to be withdrawn therefrom tosupply a demand, valves 4- and I 0 should be closed and valves 1 and I2should be open. It will be understood that means, not shown, forconsuming the fuel, 1 is attached to the end of service pipe I5 and thefuel is withdrawnirom tank I through line 5, valves and II and pipe I5to such means.

As the liquefied mixture of volatile gas withdrawn from the bottom oftank I is expanded through reducing valve II, a cooling effect is phericor lower.

produced and the vapors in chamber 8 are condensed on valve II and dropback into the container I through pipe 8. The latent heat ofcondensation of the vapors around the valve l thus supplies the heat forvaporization. of the fuel inside the valve. Accordingly, for every pound01 fuel vaporized in the valve ll, approximately one pound of vaporscondenses on 'the outside of the valve in chamber 8. The heat balance ofthis system is thus substantially the same as that ol the usual type ofsystem in which the vapors are withdrawn from the top of the container.If the reducing valve were installed outside the vapor space or thestorage tank and directly exposed to the surrounding air, substantiallyno latent heat of condensation would be available to warm the valvesince, under customary operating conditions, the temperature of the airis far removed from its condensation temperature. Furthermore, thelatent heat of condensation (and solidification) in the small amountofwater vapor generally present in atmospheric air is usually insuilicientto supply the required heat 01 vaporization. I

Inthe preferred embodiment of my invention, where the storage tank i isburied in the ground and the reducing valve II is within the vaporchamber of the storage tank, it will be apparent that heat from theground is conducted through the walls of the tank and causesvaporization of the liquid contained therein; the vapors, thus formed,continuously rise around valve II and condense thereon to furnish heatfor vaporization of the expanding liquid. To facilitate heat transfer,vanes may be provided on pressure reducing valve II.

If chamber 8 is exposed to the atmosphere, and

is not buried beneath the ground, it is desirable that it be coveredwith a suitable insulating material, such as asbestos, magnesia, and thelike. Chamber 8 is preferably also supplied with a suitable vapor-tightflanged head ll so that ready access is provided to reducing valve Hwithout releasing the contents of tank I. Thus; when it is desired toopen chamber 8 for any reason such as inspection, repairing or cleaningof resulator valve ,valve 1 in line 6 is closed oil from tank i andvalve I! in line is likewise shut oil. Valve I! in line 8 is opened torelease residual hydrocarbon vapors remaining in chamber 8. Flanged headI4 is then opened providing ready access to regulator valve ll.

It is readily apparent to one skilled in the art a that regulator valveH may be disposed in the vapor space II or the liquid space oi tank I.Though some of the same desirable eifects may be obtained as by placingit in chamber 8, it would not be possible to periodically inspect theregulator valve or to clean or adjust it without releasing thecontents'of tank i which is a very desirable feature.

Itwill be understood, that as liquefied gas is withdrawn from line I,vaporized on passin through valve "and discharged into line it to meetthe demand imposed on the system, the liquid level 2 within tank! willgradually lower leaving space into which a fresh sup y or liquefled gasmay be charged; 'When it is desired to add additional liquefied gas totank I the pressure within the tank should first be reduced to atmos Thepressure within the tank may conveniently be reduced by opening valve Itto allow equalization between tank I and the atmosphere. If desired, thepressure within tank I may be reduced to less than atmospheric byconnecting a vacuum pump, not shown, or other means for producing avacuum, to outlet 8, After the pressure within tank I has been reduced,valve 4 may be opened and the desired amount of liquefied gas chargedinto the tank through lines 3 and 5. After the tank has been charged,valves 4 and in maybe closed and. with valve l2 remaining open thedevice is in condition to supply the load, not shown, attached to linel5 as previously described.

Immediately after the tank has been installed in position, as shown inthe drawing, and contains air, it may initially be charged by fillingthe' tank with water in order to displace air from the tank and linesand the water then displaced .by the liquefied gas in order to avoid thedilution of the gas with air. Where water is used in filling the tank, apipe, not shown, with valves connected to a water supply and also to asewer is provided at the lower part of the tank in order to fill thetank before charging and to allow the water to drain during the chargingof the tank with. the liquefied gas.

By operating a storage and dispensing apparatus for liquefied gases inthe manner set forth herein, numerous advantages over the conventionaltype of dispensing and storage apparatus may be obtained. By operatingin accordance with this invention, it is possible to vaporize liquefiedgases containing traces of moisture without freezing the regulatorvalve, Another advantage accruing to this invention is that mixt'ures ofliquefied gases may be employed which on vaporization will give a vapormixture of substantially the same composition as the liquid mixtures;thus, when a major portion of the contents of a drum such as disclosedin the drawing has been vaporized, the remaining portion issubstantially of the same composition and vapor pressure as that of theoriginal drum contents. When the apparatus which has been describedherein is located out doors and below the ground, the method ofoperating the same will overcome cold weather difficulties which areinherent in conventional types, of apparatus.

In many conventionalstorage and dispensing systems for liquefied 'gasesit is necessary that external sources of heat be provided; in the systemwhich is the subject matter of this invention, an extraneous source ofheatsupply is not needed if the storage drum is buried beneath thesurface of the ground and is otherwise uninsulated. Besides havingavailable the sensible heat of the vaporized hydrocarbons-in tank I andchamber 8 surrounding pressure regulator valve II, there is alsoavailable the latent heat of vaporization which, when compared to thesensible heat of air in the atmosphere, is considerable. Under usualconditions of operation when the apparatus is buried below the frostline of the earth, suillcient heat to vaporize the hydrocarbon is madeavail.- able. A constant supply of gas will thus be assured underconditions which would otherwise prevent the efilcient operation of areducing valve located externalLv from the drum.

I claim:

1. In a liquefied gas storage and dispensing system, a service pipe, apressure storage tank arranged with an eduction conduit communicat- 8 atone end with a point adjacent to the bottom of the tank, a pressurereducing valve arranged in a separate chamber adjacent to the top of thetank and connecting the opposite end of the induction conduit with theservice pipe, a tube extending from the separate chamber to the 2.3mm t3 upper part of the said storage tank and prodding direct communicationbetween the separate chamber and the upper part of the said storagetank.

2. A method of dispensing gas stored es o 5 liquid under preseure whichcomprises withdrewing from a body of liquefied gas maintained underpressure in a container, a, port of the liquefied gets, passing thewithdrawn port of the liquefied.

get through a, reducing valve maintained in direct heat exchangerelationship with vapors given

